Optical parameters such as total and diaphragm transmission and diffuse reflection have been investigated by in vitro set up for whole blood. Original construction cuvette allows change thickness of a layer inside without removing of content. Changes of the blood concentration have been created by dilution of centrifuged blood. Hematocrit, hemoglobin and oxyhemoglobin concentration have been measured simultaneously by independent methods. According to the received data the coefficients of scattering and absorption and the average cosine of scattering are calculated for whole blood by the Monte-Carlo simulations. The curve of light penetration into whole blood is created for the following wavelengths: 488, 587, 633, 675, 820, 860 nm.